The present invention relates to a method for producing hydrogen from light hydrocarbon paraffins, separating the hydrogen from the effluent product, and, if desired, hydrogenating heavy unsaturated hydrocarbons with said hydrogen.
At the present time, the hydrogen requirements of petroleum refineries, which are necessary for hydrogen treating operations, such as hydrogenation, hydrotreating, hydrocracking, etc., and for the production of petrochemicals, are extremely high. Hydrogen requirements are even higher in processes for treating liquids of a hydrocarbon nature which are highly unsaturated, such as liquids derived from coal. For example, coal liquids may be obtained from coal by carbonization or pyrolysis of the solid coal to produce coal tar products or by the solvent extraction of solid coal, with solvents such as tetralin, decalin and the like to produce a solvent extract, or combinations of these techniques. The hydrocarbon liquids produced from coal are extremely complex, generally cyclic or aromatic compounds, having a high degree of unsaturation or hydrogen deficiency. Consequently, in order to process such liquids further, it is necessary to stabilize such liquids by at least partial saturation so that they may be handled in high temperature equipment, both in distillation and catalytic processing, without extreme coking, plugging, etc. It is also necessary that such coal liquids be at least partially saturated in order to produce so-called synthetic petroleum which can then be processed in conventional manners in a petroleum refinery for the production of the usual petroleum-type products and, in some cases, some unusual products.
At the present time, the production of hydrogen for the petroleum-petrochemical industry is generally through the catalytic reforming of naphthas or the steam reforming of light hydrocarbons. The hydrogen available from catalytic reforming is rather limited and in short supply, so that more and more producers are resorting to steam reforming of light hydrocarbons to satisfy the massive hydrogen requirements of today's operations. However, even this technique has fallen short of today's demand of the petroleum refinery and it is nowhere near adequate for the production of hydrogen for the saturation of coal liquids. Another method for producing hydrogen is as a by-product of the production of unsaturated hydrocarbons. One such process involves the pyrolysis of hydrocarbons to produce products such as acetylene, ethylene and propylene. This system has the disadvantages of high temperature and low purity of the hydrogen stream. Another possible source of hydrogen is as a by-product of processes for the dehydrogenation of saturated hydrocarbons to produce the corresponding unsaturated hydrocarbons. While this is a relatively simple operation and large quantities of the saturated hydrocarbons are available as a raw material and at reasonable prices, these processes which have been developed have numerous drawbacks. For the most part, the processes developed to date are cyclic, adiabatic, fixed-bed, regenerative processes operating on short cycle times due to coke deposition on the catalyst. Typically, the cycle times in these cases are about 7 to 15 minutes. Therefore, for a continuous operation, a minimum of three reactors is required with one reactor on-stream, one being regenerated, and one on standby. Multiples of this system can be utilized to increase production.
It is therefore an object of the present invention to provide a process which overcomes the above-mentioned difficulties. Another object of the present invention is to provide a process for the production of substantial quantities of hydrogen. Another and further object of the present invention is to provide an improved process for the production of substantial quantities of hydrogen from light paraffinic hydrocarbons. Still another object of the present invention is to provide an improved process for the production of hydrogen by contacting light paraffinic hydrocarbons with a highly effective catalyst. Yet another ojbect of the present invention is to provide an improved process for the production of hydrogen by the dehydrogenation of light paraffinic hydrocarbons, separation of hydrogen from the effluent product and hydrogenation of coal liquids with the recovered hydrogen. Another and further object of the present invention is to provide an improved process for the production of hydrogen by contacting light parafinic hydrocarbons with a novel catalyst capable of extremely long cycle periods. A further object of the present invention is to provide an improved process for the production of hydrogen, including dehydrogenating light paraffinic hydrocarbons, liquefying the effluent product and recovering the hydrogen from the liquefied product by flashing a dry gas portion containing hydrogen therefrom. Yet another object of the present invention is to provide an improved process for the production of hydrogen wherein light paraffins are dehydrogenated, the effluent product is liquefied, the dry gas portion of the liquefied product is flashed to recover the hydrogen, and the hydrogen is further purified by the removal of other gases therefrom. A still further object of the present invention is to provide an improved process for the production of hydrogen wherein light paraffins are dehydrogenated, the effluent product is liquefied, the dry gas portion of the liquefied product is flashed to remove hydrogen therefrom and the remaining liquefied product is distilled to separate saturated from unsaturated products. Another object of the present invention is to provide a process for the production of hydrogen wherein light paraffins are dehydrogenated, the effluent product is liquefied, the liquefied product is flashed to remove the dry gas portion including hydrogen therefrom, the remaining liquefied product is separated into saturated and unsaturated fractions and the saturated fraction is recycled to the hydrogen production step. These and other objects and advantages of the present invention will be apparent from the following detailed description.